The scene is repeated in almost all kitchens. Grapes in the colander, apples under the tap, a spoonful of bicarbonate to feel a little calmer. That gesture has within it an ancient, domestic, almost automatic trust. Then the data arrives and the ritual changes face. A group of researchers at the University of British Columbia have developed a fruit washing which, in tests on apples, removed between 86 and 94% of surface residues of three common pesticides; tap water, bicarbonate and simple starch stopped below half. The study was published on ACS Nano.
The idea brings together very ordinary things and a rather refined chemical construction. The base is starch, the same carbohydrate found in corn and potatoes. The researchers transformed it into microscopic particles and coated it with iron and tannic acid, the plant compound that gives tea and wine that dry sensation on the palate. When iron and tannic acid bind, they form porous, adhesive aggregates that stick to pesticides and lift them off the surface of the fruit.
The team applied three common pesticides to apples at concentrations considered realistic, around 10 milligrams per liter. From there the comparative test started. The new rinse showed a removal capacity of between 86 and 94%, with a clear difference compared to the most used home methods. It is the point that makes the research interesting even outside the laboratory, because it touches on an everyday gesture and gives it a concrete measure.
Then comes the second step, the most surprising one. After washing, the fruit is immersed in the same solution again and a edible film light and biodegradable. On cut apples, this barrier slowed browning and water loss for two days in the refrigerator. On whole grapes the result was even more visible: the treated grains remained firm for 15 days at room temperature, while those left without coating showed signs of failure first. The coating also provided antimicrobial effects, useful in containing the growth of harmful bacteria.
Another strong point lies in the costs. The group’s initial estimates are around three cents per applea figure close to that of commercial coatings already used in industrial processing, with the added advantage of removing residues. The iron transferred to the fruit, according to the researchers, remains at levels considered safe and well below the maximum daily limit indicated by the North American authorities.
From the industrial supply chain to the home kitchen
The first realistic destination remains industry. The ingredients are cheap, they are mixed in water and the process lends itself well to facilities where fruit is cleaned before shipping. The group is working on precisely this: refining the formula, scaling it up and testing it on more types of fruit. In the background there is also a kitchen version, perhaps in the form of a spray or tablet to be dissolved in water just before rinsing. That step, however, requires further studies, real-use trials and regulatory approval.
The topic, in Italy, remains very concrete. In the 2024 Legambiente dossier, built on the samples analyzed in 2023, 41.32% of the foods examined showed traces of one or more pesticide residues, with 26.33% of multi-residues. Fruit was the most exposed category, with 74.11% of samples affected. In the chapter dedicated to grapes, the Italian laboratories detected at least one active substance in 64.03% of the 139 samples analyzed, with a prevalence of multi-residue over single-residue.
This is where this fruit washing finds its true weight. Bicarbonate remains a widespread, reassuring, simple gesture. The Canadian research tells something more precise: the removal of residues can become much more effective without adding impossible complications, and in the same movement it can prolong the freshness of the product. There is still a road between the laboratory and the sink, but the direction can be seen clearly. This time it shows on the peel.
